Allow entering dates with `0` as month or day

[grantfitzsimmons]

I have wood turtle records with an observation year, but no day or month. When I try to fill in the Identification, Start and End Date fields, I am unable to fill out just the year, leaving the month and day as 0. E.g. 1966-00-00. Specify auto-fills the day and month as 01, so my date appears as 1966-01-01.

It could automatically change the format accordingly.

If someone entered 1966-00-00, it could automatically switch to "Year" as the precision

Requested By: New Brunswick Museum